How to get fixed buffer length?

Question

Is there a way to get the length of a fixed size buffer?

Something like:

public struct MyStruct
{
    public unsafe fixed byte buffer[100];

    public int foo()
    {
        return sizeof(buffer); // Compile error.
    }
}

Is there any way to accomplish something like this?

Answer 1

Well like in C++, you have to keep size of built-in arrays. Same applies for fixed buffers in C#. This type is comparable to inline_array. This gives you benefits such as static code checking. They are a bit of a pain to work with as they aren't C#'s first class feature. So probably the best solution is to keep size as a part of struct. You will probably just have to deal with it or use a collection/C#'s System.Array. Maybe another solution would be to create fixed buffer as a seperate struct and then make it part of another stucts with other data.

Answer 2

Well, I'm answering like 6 years late but I did this. Apparently there's a property that contains the length of the fixed buffer! Here's a simple method to get it. You need to pass the MyStruct type and the name of the field:

    public static int GetFixedBufferSize(Type type, string field)
    {
        FieldInfo fi = type.GetField(field);
        object[] attrs = fi.GetCustomAttributes(typeof(FixedBufferAttribute), false);
        if (attribs != null && attribs.Length != 0)
        {
            FixedBufferAttribute attr = (FixedBufferAttribute)attribs[0];
            Console.WriteLine($"{attr.ElementType.Name} {field}[{attr.Length}]");
            return attr.Length;
        };

        throw new Exception("Not a FixedBuffer");
    }

Hopefully this works for you, I tried it with your example and it worked!

Answer 3

That's an array; you can just use .Length.